Authorities say the toddler was left in the care of 22-year-old Dakota Miller in Hornell and sustained an unspecified injury last week. Hornell is in Steuben (stoo-BEHN') County, about 60 miles south of Rochester.

Miller was charged with assault before the child's death. Authorities say they will consider upgraded charges once the medical examiner finishes an autopsy.

It's unclear if Miller has an attorney who could comment on the charges.